Electroporation is a technique used for introducing molecules across a cell membrane and into a cell. In a typical application, an in-vitro cell culture is mixed with a target molecule and a brief electrical field is applied to the mixture. The electrical field causes a transient porosity of the cell membranes, allowing the molecules to enter the cell. U.S. Pat. No. 5,501,662, the disclosure of which is incorporated herein by reference, describes an electroporation system for blood, in which an electric field is applied to a vessel having blood cells mixed with a target gene (or other molecules) and the electric field causes the genes to be transported into the cells. Electroporation is especially useful for large molecules, such as proteins, and for other molecules which do not have a biological mechanism for crossing the cell barrier.
Iontophoresis is a method of transporting drugs into a body tissue, from outside the body tissue, usually from the skin. The drug is provided in a charged form and, when an electric field is applied, the electric field moves the charged drug along the gradient of the field.
PCT publication WO98/15317, the disclosure of which is incorporated herein by reference, describes an implantable drug-eluting tip which uses a cardiac pacing signal to cause charged drug particles to leave a reservoir and be available locally. It is suggested in that publication that the electric field of the pacing signal is sufficient to iontophorese the drug into the heart tissue. Injection of DNA into individual cells is suggested using a similar device, for apply toxins to tumor cells, apparently not in the heart. However, it is not clear whether the fields strengths and durations of a pacing signal are sufficient for electroporation or even iontophoresis for any considerable depth.
U.S. Pat. No. 5,865,787, the disclosure of which is incorporated herein by reference describes a catheter for electroporation or iontophoresis, in which the iontophoresis pulses are applied in conjunction with active pacing.
U.S. Pat. No. 5,387,419, the disclosure of which is incorporated herein by reference, describes a system for controlled release of antiarrhythmic agents.